For example, Patent document 1 discloses an inverter device (inverter controller) that is able to continue conversion of electric power for transmitting to a load even if an instantaneous voltage drop occurs in the electric power system. In the conventional technology disclosed in Patent Document 1, when an instantaneous voltage drop occurs in the electric power system, the direct-current-bus voltage and the current input to the inverter device are detected and a feedback control is performed such that the direct-current-bus voltage of the inverter device attains a certain desired voltage based on the detected direct-current-bus voltage and the detected input current. In addition, the output frequency of the inverter device is adjusted such that the input current meets a controller output of the direct-current-bus voltage. Accordingly, the inverter device is able to continue driving a load without stopping even if an instantaneous voltage drop occurs.
Patent Document 1: Japanese Patent Application Laid-open No. H4-317592